Does anyone know the album Moonstone shapers mark for fin measurements and or the width of the swallow… Or any other deets. Can’t get my hands on one here where I live.
Mate wants something similar,I will make for him but doesn’t want pay that huge price of the moonstone.
Cheers
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Did you watch the videos on the Album website?
Not exact numbers but a pretty good ‘lay of the land’
From the photo and what I know about albums it looks like right around the 9” mark for both questions. What’s the length and width of the board you’re wanting to do.
It’s going to be 6’4 x 19 3/4.
Blokes going run an upright keel sort of fin as suggested.
I was thinking about 9 1/4. 1 3/16 from rail and 3/16 toe. but with the upright keel maybe thinking back a bit.
Really didn’t have time for this.
But since I have been a student of the Retro Fish for several years…
From the Moonstone website, the board in the photo is 19" x 6’2" (74").
Based on that width and the graphics, I get an estimate of 9.65" wide at the wing tips.
The general formula for a Retro buttcrack depth is 1/2 width at wing tips which would give you a buttcrack depth of 4.83".
However, if I use the graphics dimensions to estimate buttcrack depth I get 5.72".
Draw it full-scale and see which dimensions look most correct.
Assuming some lens distortion, I would guess the buttcrack depth x wingtips width is 6" x 10" for a 6’4" (76") board.
(Those should be close enough for shaping purposes.)
Accept. Reject. It does not affect me.
Add this to my previous post and,
Distance from wingtip to rear of fin “slot” measures very close to the same as width at wingtips.
Outside rear end of fin “slot” appears to be 1” from the rail.
(Photo is screenshot from video for the same board above.
Correction;
‘Outside rear end of fin “slot” appears to be 1.73” from the rail.’
‘End of fin slot 10.38" from wing tip.’
I get a little different result using the length of a Futures fin box to establish scale in the image and trying to use the stringer as the straight line reference/ axis.
-fins closer to rail
-fins closer to tail
-width of tail
Jim,
I’d say fin distance from rail measurement is pretty much the same (yours vs. mine, 1.73 vs 1.75). The distance you measured (start and end points) is slightly greater than mine.
I figured somebody like you might notice the discrepancy.
Problem using that image is that it is a bottom shot. The shot is from a video (spinning on the toe of a young woman). Because it is a bottom shot it has much more rocker, arching rearward. She appears to be holding the board with a backward lean also. And because it is spinning on a person’s toe there is some slight lean to the right (which you can detect when you measure the angle of the fin slots — I tried for toe-in estimate, too in accurate). Bottom line, the longitudinal measurements are likely to be more distorted in this screen shot.
The first photo is taken as a still shot and the bottom (flatter) tail rocker against the wall. Board is more carefully posed. Greatest (nose) rocker is placed at the bottom (floor), nose away from the wall. Much flatter tail rocker (flat against the wall transversely). Board is more carefully placed vertical (perpendicular) to the ground (no axis/spin distortion). I always use deck shots for planshape (much flatter deck rocker).
But most important IMO, with board bottom transversely flat against the wall (no spin angle in particular), width (transverse) measurements are not distorted relative to one another. The relationship (ratio) to one another is not distorted. And what we know for certain is board width is 19”.
Finally, the buttcrack distance is the shortest length measurement on the Deck (flattest against the wall), being least distorted by any lean.
This is why I consider board width and wingtip width measurements (deck-side photo) the most accurate, relative to the 2 pictures.
I consider the dimensions I generated with the bottom video shot of the board being spun to be the least accurate. ( Also, I enlarged the tail image which reduced resolution further.)
I only used the bottom (video) shot to get a general/relative feel of fin placement.
Definitely go more than 1 3/16” off rail. I would do 1 1/2” and 3/16 toe like you were thinking. That’s what I use on most twins
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No challenge intended.
Won’t fin distance from wingtips affect fin placement relative to the rail?
I was not intent on throwing the glove down either, so to speak, just illustrating the process I would use on a small image that is not square to the world. I am convinced that not every image of every surfboard for sale online is 100% to scale to the stated length x width that they are meant to represent. In such a case, or where the photo is angled, a known size object can be useful for considering the major details +/- whatever the pixels allow.
I probably would have taken @MRat 's initial ‘inkle’ and started to run with it.
Someone please remind me: the shaper’s mark goes on the inside edge of the rail fins, starting at the back of the slot and running foward 4 or so inches, yes?
It’s been a minute, OK 3 some years, since I have routed in set of boxes…
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Ya rear inside (closest to stringer) and 4.5” for futures.
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No question!
Even with carefully posed upright board mounting, there is obvious lens distortion.
The posed still shot I used displays obvious lens distortion when looking at the the seam lines of the cinder blocks in the wall. (To make things worse, many photos used are taken with cell phone cameras which are notorious for lens distortion caused by shot angle.)
So, if the full rocker arc leans back from the point on the holder’s toe, the known fin box length will be shorter in a 2D photo.
So, I like to find/use a dimension least likely to be affected by distortion. In this case, for wingtip width, horizontal/transverse ratios using max. board width from a deck view with tail placed flat against the wall.
Another concern I have is fin placement relative to wingtip points.
For a Retro Fish, fins are aligned relative to wingtip positions.
Therefore, the farther the fins are from the wingtips, the farther the rear base of the fin will be from the rail.
EDIT:
This is the Moonstone link I used,
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I had to know. So I contacted Album Surf through their website about their 19” X 6’2” Moonstone SB.
They measured width at the wintips for me. The distance was 23 cm apart (9.06 in).
Wingtip separation I measured from the still photo is 1.065 times greater than actual.
So based on their 23 cm measurement and ratios measured from the still photo, tail dims would likely be;
Wing tip separation = 9”
Buttcrack depth = 5.44”
Distance from wingtips to base of fin = 9”- 9.5”
(However, as board width changes, tail dims will change.)
I’ll leave the rest to others.
EDIT:
Beyond distortion, as Jim mentioned, the board pictured may not be the actual 6’2” Moonstone.
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Calling the manufacturer, cutting to the chase!
Thanks everyone for your input.
All the Intel was around my numbers
So my only question is now.
My mate has got a fin base of 6.2 inches. Upright keel by Captain fin co he says
So I’m thinking running the futures box at 9.25 but in from rail what ever lines up with the trailing edge of the fin at 1 3/16
I’ve always been told to work around the 9.25 mark for a twinny if more performance orientated and my small fishes are just forward of the crack.
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I’m no pro on fin placement.
But IMO the Moonstone is a swallowtail.
(Placement of keel fins for a “Fish” is more specific.)
I have seen a wide range of recommendations for twin fin placement.
Seems like board length is a factor also.
Starting first with this old Sways thread;
Retro/Lis Fish Keel (from Kinstle book)
From Greenlight Supply
From Fiberglass Hawaii
Hanalei Fins Swallow
For grins, Hanalei Fins Kneeboard Twin
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Hey hello, congrats on the Coanda Board.
Now regarding the topic, mainly the fiberglass hawai chart (i really like it).
i posituon the fin bixes one inch or one inch and a quarter from the rail, is this good measure or you have another sugestion in how to do it?
cheers and good waves.
Thanks.
I have researched twin fin placement over the years but haven’t ridden a twin in decades. My interest has been/was for Fish design purposes. The Fish design platform is well suited to some of my foil concepts/ideas.
Because there are so many different recommendations, I have no personal opinion about twin fin placement relative to the rails.
First, it has been my take that fin placement close to the rail and forward was needed for shorter boards because there is less rail to generate a keel effect on hard lean turns. Second, IMO, fins close to the rails create a pivot point to tighten turning radius for high centrifugal force turns. In both cases, they would/should mitigate side-slipping/drift.
Finally I changed direction to finless when I came up with the Coanda Channel design several years ago. (But I do still like the Retro Fish twin concept.)